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Homework Help: How to calculate current of a resistor inside of another parallel resistor?

  1. Feb 28, 2007 #1
    How to calculate current of a resistor "inside" of another parallel resistor?

    The 1st image is how he drew it for us, no text.. I guess because it's quite complicated.
    He asks a bunch of questions, I've answered..
    1. Equivalent resistance of R3 and R4=5 ohms
    2. combined resistance of R6 and R7=9 ohms
    3. combined resistance of R9 and R10? =9 ohms
    4. equivalent resistance from D to E? 3 ohms
    5. Equivalent resistance from B to E?
    ---
    this one was kind of tricky.. but I think I got it right.. 5 ohms? I calculated the equivalent resistances of R(3,4) and R(6,7,8,9,10), added it to R5.. Now, R(3-10) acts parallel to R2... blah blah, 5 ohms for R(2-10).
    6. total resistance? 5 ohms of the parallels and 2 and 1 makes 8.
    7. total current? 3A
    8. Potential drop occurs across R1? 6V
    9. Drop in potential from B to E? 15V
    10. Current in R2? 1.5A
    :confused: 11
    Current in R5? How come I got R2 but not R5?
    "9. Drop in potential from B to E? 15V"
    Vt in parallel is equal to "everything", by everything, meaning "one and one".. or something.. So yeah, I'm positive that V2 is 15V.. and V(3-10) is 15V.. But how do I find the V5 to find out the I5.. Thanks..
    --
    Also just figured that I(3-10)=1.5A..
    "$ 1 5.0E-6 10.391409633455755 50 5.0 43
    w 64 368 64 208 0
    v 64 208 64 176 0 0 40.0 24.0 0.0
    w 64 176 64 96 0
    w 64 96 144 96 0
    r 144 96 176 96 0 2.0
    w 176 96 272 96 0
    w 272 96 272 192 0
    r 272 192 272 240 0 10.0
    w 272 240 272 368 0
    w 272 368 208 368 0
    r 208 368 176 368 0 1.0
    w 176 368 64 368 0
    w 272 96 480 96 0
    w 480 96 480 112 0
    w 480 112 416 112 0
    w 480 112 544 112 0
    r 544 112 544 144 0 10.0
    r 416 112 416 144 0 10.0
    w 416 144 480 144 0
    r 480 144 480 176 0 2.0
    w 544 144 480 144 0
    w 480 176 544 176 0
    w 480 176 416 176 0
    r 416 176 416 192 0 7.0
    r 544 176 544 192 0 6.0
    w 416 192 416 208 0
    w 544 192 544 208 0
    r 416 208 416 224 0 2.0
    r 544 208 544 224 0 3.0
    w 416 224 480 224 0
    w 480 224 480 208 0
    r 480 208 480 192 0 9.0
    w 480 176 480 192 0
    w 544 224 480 224 0
    w 480 224 480 368 0
    w 480 368 272 368 0"
    http://www.falstad.com/circuit/
    This has confirmed my other answers.. still wanna know number 11 and past, how to do them.
     

    Attached Files:

    Last edited: Feb 28, 2007
  2. jcsd
  3. Mar 1, 2007 #2
    Meh.. anyhow, I came upon kind of a breakthrough..
    I got 15V for the voltage of the non serialized resistors.. An in a parallel, all "total" resistors have equal voltage.. So V2 equals V(3-10[sans 2])
    15V=V2=V(3-10[sans2)..
    With V2, and te given R2, I got I2 of 1.5A.. and in a circuit, total current is equal to current of the series, or the sum of the parallel's.. So if It=3A..and I2=1.5A.. V(3-10[sans2])=1.5A.. and since R5 is in a series with R(3-4), R(6-10), it's current is equivalent to the other's.. So V5=1.5A?? And yeah..couple hours til I get to his class anyhow..
     
  4. Mar 1, 2007 #3
    Case closed..and the rest of the answers that I came up with match the falstad.com data thing;;:)
     
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